1. Field of the Invention
This invention relates generally to automatic washing machines and is concerned more particularly with an automatic clothes washing machine having an additive fluid dispenser system powered by a source of direct current.
2. Discussion of the Prior Art
In the loading of an automatic washing machine, clothes generally are deposited through an access door into an open end of a perforated spin tub which is rotatably supported in a stationary drain tub within a cabinet. The washing machine may be cycled through a sequence of operations including a presoaking operation followed by a first liquid extraction, a washing operation followed by a second liquid extraction, a rinsing operation followed by a third liquid extraction, and a spin drying operation. For any of these operations, an additive fluid may be injected into the wash load to enhance the results of the associated operation.
Consequently, there has been developed in the prior art a number of additive dispensing means having respective housings disposed for holding additive liquids until released for a particular operation of the wash cycle. For example, in a patent application filed concurrently herewith by R. L. Bisplinghoff, et. al and assigned to the same assignee, there is disclosed an additive fluid dispensing means comprising a multi-load reservoir of additive liquid connected through a pumping means to a stream ejecting nozzle. The additive liquid may comprise a conventional liquid soap having a viscosity which varies over a wide range of temperatures. Also, the pumping means includes a constant displacement pump, such as a vane type pump, for example, which is driven by an electrical motor.
For the described fluid dispensing means, the motor driving the pump usually is of the alternating current type because of the simplicity in design resulting from having the motor energized from the same alternating current source used for operating the washing machine. However, the advantages, thus gained, may be outweighed by the comparatively large size of the alternating current motor required for delivering the torque necessary to pump high viscosity liquids, such as relatively cold liquid soap, for example. An alternating current motor of this comparatively large size may be regarded as unduly expensive in view of the task it performs, namely, driving a constant displacement pump so that additive liquids with temperature sensitive viscosities may be injected at a uniform rate into a spin tub of a washing machine.
In selecting the type of electrical motor best suited for the described fluid dispensing means, one factor that should be taken into consideration is the relatively short duty cycle of the motor. It is expected that the motor will be energized to drive the pump for only a brief period of time, such as about thirty seconds, for example. This period of time should be sufficient for injecting an adequate quantity of additive liquid, such as soap, for example, into a spin tub for processing a single wash load.
Another factor that should be taken into consideration when selecting the motor for driving the additive pump is the life expectancy of the motor. It is anticipated that the washing machine will be used for processing a wash load on the average of eight times a week over a period of about eleven years. Thus, the life expectance of the motor is approximately thirty-eight hours of operation.
Therefore, in view of the relatively short duty cycle and life expectancy of the motor driving the pump, it may be argured that the alternating current motor of comparatively large size mentioned above is not the most cost-effective mean for performing the described function.